A touch panel is an input device that allows input to be performed directly on a display. The touch panel is often used by being placed at the front of a display. Because input can be performed directly on the touch panel based on data that is visually recognized from the display, the touch panel can be used for various purposes.
Among the touch panels, a resistance type touch panel and a capacitive type touch panel are widely known. The resistance type touch panel, which includes upper and lower electrode substrates, has a transparent conductive film formed on each of the upper and lower electrode substrates. The transparent conductive film of the upper electrode substrate and the transparent conductive film of the lower electrode substrate are positioned facing each other, so that the transparent conductive films contact each other when force is exerted on a single point of the upper electrode substrate. Thereby, the position at which force is exerted can be detected. The capacitive type touch panel can detect a position of the touch panel by detecting a current that flows in, for example, a transparent electrode of the touch panel when a finger or the like is brought near the touch panel.
Generally, a decorative film is adhered to a surface of the touch panel. The decorative film includes a printing layer formed in a peripheral part of the touch panel serving as a decorative layer. A method for manufacturing a touch panel adhered with the decorative film is described with reference to FIGS. 1 and 2.
The structure of the touch panel illustrated in FIG. 1 includes a touch panel body 910 and a decorative film 930 that are adhered to each other by way of an OCA (Optically Clear Adhesive) 920. The decorative film 930 includes a transparent substrate 931 and a decorative layer 932 formed on a surface of a peripheral area of the transparent substrate 931. The decorative layer 932 may be formed with, for example, a coating that prevents light from transmitting therethrough. Further, a flexible printed circuit (FPC) 911 is connected to the touch panel body 910 for transmitting electric signals or the like.
In a case of manufacturing the touch panel having the structure illustrated in FIG. 1, the OCA 920 is to be adhered on the decorative film 930 as illustrated in FIG. 2A. A notch 920a is provided in the OCA 920 for preventing the FPC 911 from adhering to the OCA 920.
Then, as illustrated in FIG. 2B, the OCA 920 and the decorative film 930 are adhered to each other. Thereby, the touch panel having the structure illustrated in FIG. 1 is manufactured.
FIG. 3 is an top plan view observed from a direction of viewing the touch panel manufactured as described above. The process drawings of FIGS. 2A and 2B are cross-sectional views taken along a double-dot dash line of FIG. 3.
[Patent Document 1]: Japanese Laid-Open Patent Publication No. 2012-203514
With the above-described method for manufacturing a touch panel, the notch 920a is to be formed in the OCA 920. Therefore, the above-described method requires a process of forming the notch 920a and a mold for forming the notch 920a. This leads to increase of manufacturing cost. In a case where the notch 920a is not formed in the OCA 920, the FPC 911 connected to the touch panel body 910 may adhere to the OCA 920. Thus, in a case where thermal expansion occurs in the touch panel body 910 and the decorative film 930 in a state where the FPC 911 is adhered to the OCA 920, stress is generated by the thermal expansion difference between the touch panel body 910 and the decorative film 930. The stress may cause the FPC 911 to peel from the touch panel body 910 and lead to failure and malfunction.
Further, in a case where the decorative layer 931 of the decorative film 930 is thick, rugged (convex-concave) areas may be formed on the surface of the OCA 920 adhered to the decorative film 930. This may cause difficulty in neatly adhering the touch panel body 910 to the decorative film 930 and adversely affect the appearance of the touch panel. Further, if the OCA 920 protrudes from the touch panel body 910 or the decorative film 930, dust or the like may adhere to the protruding part of the OCA 920. Such dust or the like not only degrades the appearance of the touch panel but also degrades the yield of the touch panel.